Black and white to RGB - how to?

joeycuda

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I know this has been done, but I am finding very little information. I want to use a WG4900 color monitor in a Space Zap mini, which would need a 13" b&w. Bought it with monitor missing. I have the color monitor, so would like to use it instead of hunting for the b&w.

I've found the following in googling RGVAC archives-
1) Tie RGB together
or
2) Tie RGB together, but after each line going through a 100ohm resistor.

What is the best and correct way to do this?

Thanks in advance...
 
I tested some old Atari b/w boards on an Amiga color monitor by connecting the videosignal of the PCB to RGB+Sync(+GND?) of my Jamma Supergun. Picture is not as sharp & bright as with a b/w monitor but it works.
 
I once bought a Lunar Lander PCB off eBay. The guy had a picture on his auction site which showed the vectors in green.

I asked him how he did that. He said

"I have a special test rig made by Atari called a 'PAT 9000'.. it has factory-made harnesses to test boards such as Lunar Lander and it came pre-wired.. but a color monitor has the exact same inputs as a B/W one.. it only has 3 inputs for the colors instead of just one. If you want to connect it to a color monitor, just connect the signal (Z output) to the green gun only and it will work fine, the screen will be green just like in my pictures. If you want it to look white, you can mix the board's output into the 3 colors using resistors, but I do not have any info on how to do this.. the net or collecting newsgroups may have that sort of info."

His name is Jeff Anderson, maybe he is known here on the forum
 
I spent a good bit of time playing with the RGB inputs on a K4915 recently. Taking any one RGB signal line and feeding it to another input (or set of inputs) yielded the color expected, including white (R+B+G). You can test it if you like simply by bridging RGB at the chassis input, the neckboard feed, or even the KR, KB, KG on the tube socket.

The only reason I can think for adding resistors is that three drive circuits in parallel may drop resistance enough to allow too much current through the output section B&W drive circuit. If that's a concern, you could always feed the BW signal to a single color input on the chassis and then decouple the "dead" colors at the tube neck and feed the "live" color channel to all three guns.
 
Thanks for the responses. I think this will get me there. I'm picking up the Space Zap very soon, have a switcher adaptor, and this info should really help me get it going!

Thanks...
 
Nice topic guys...

Im totally worried about my SI monitor dying and i have plenty extra color monitors laying around.

Would like to know how this turns out.
 
I know this has been done, but I am finding very little information. I want to use a WG4900 color monitor in a Space Zap mini, which would need a 13" b&w. Bought it with monitor missing. I have the color monitor, so would like to use it instead of hunting for the b&w.

I've found the following in googling RGVAC archives-
1) Tie RGB together
or
2) Tie RGB together, but after each line going through a 100ohm resistor.

What is the best and correct way to do this?

Thanks in advance...

Well, if I were you, I'd hack the game board to make it play in color rather than kludging the color monitor to use black & white.

In general to hook composite up to RGB, you can just run the composite signal to red. green, blue, and add in a low-pass filter with a ~15.7khz cutoff frequency to pull the csync out of the composite. (hsync is ~15.7khz, vsync is ~60 hz, video data is usually at ~5Mhz).

In the case of space zap, the cpu board puts out Y, B-Y, R-Y signals like the "other" astrocade games, but only the Y gets buffered and output on the game board.

If you make copes of the buffer circuit (Q5, R40-42) for B-Y and R-Y and run thouse out, you can get an astrocade rgb interface board to convert Y, B-Y, R-Y to R, G, B, Sync, and hook it up to a color monitor in color :)

(But that's probably more work than you want to put into it).
 
Well, if I were you, I'd hack the game board to make it play in color rather than kludging the color monitor to use black & white.

In general to hook composite up to RGB, you can just run the composite signal to red. green, blue, and add in a low-pass filter with a ~15.7khz cutoff frequency to pull the csync out of the composite. (hsync is ~15.7khz, vsync is ~60 hz, video data is usually at ~5Mhz).

In the case of space zap, the cpu board puts out Y, B-Y, R-Y signals like the "other" astrocade games, but only the Y gets buffered and output on the game board.

If you make copes of the buffer circuit (Q5, R40-42) for B-Y and R-Y and run thouse out, you can get an astrocade rgb interface board to convert Y, B-Y, R-Y to R, G, B, Sync, and hook it up to a color monitor in color :)

(But that's probably more work than you want to put into it).

[edit] Never mind, I found the answer.

The 15kHz low-pass filter can be done with a simple R-C circuit. Lots of websites out there describe how to make one.
 
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Well, if I were you, I'd hack the game board to make it play in color rather than kludging the color monitor to use black & white.

In general to hook composite up to RGB, you can just run the composite signal to red. green, blue, and add in a low-pass filter with a ~15.7khz cutoff frequency to pull the csync out of the composite. (hsync is ~15.7khz, vsync is ~60 hz, video data is usually at ~5Mhz).

In the case of space zap, the cpu board puts out Y, B-Y, R-Y signals like the "other" astrocade games, but only the Y gets buffered and output on the game board.

If you make copes of the buffer circuit (Q5, R40-42) for B-Y and R-Y and run thouse out, you can get an astrocade rgb interface board to convert Y, B-Y, R-Y to R, G, B, Sync, and hook it up to a color monitor in color :)

(But that's probably more work than you want to put into it).

Now, that's some good info. Thanks Mark. For NOW, that's more than I want to put into it, but I would like to attempt that in the future.

I picked it up last night. I plan to stick a switcher in there this weekend just to see if it will play blind. The control panel restoration will be interesting. Cosmetically, it should turn out pretty nice.
 
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